As with studying the elements of any piece of literature, identifying symbols is open to wide interpretation. We are responding to a piece of art, something each of us will react subjectively to because of our personal experiences and interpretations. The test to identify symbols in a piece of literature is based on the reader's ability to find examples in the text that provide a deeper meaning to the story through the use of the symbols.
In comparing Rue and Prim in Suzanne Collins' The Hunger Games, there seems to be evidence that Prim might symbolize innocence. However, from what I know of her character, Rue does not.
Prim is defenseless. Others in the arena that are young and inexperienced like Prim die immediately. In her heart, she is a frightened child. Using indirect characterization, Katniss' overwhelming need to protect Prim allows the reader to view Prim through the eyes of someone older and better seasoned to the harsh realities of life in Seam.
I protect Prim in every way I can, but I’m powerless against the reaping. The anguish I always feel when she’s in pain wells up in my chest and threatens to register on my face. I...force myself to stay calm.
One might argue that Rue is more experienced because she has been training for the games. However, what we see of Katniss' strengths were already present before she arrived at the Capitol; she shows that she has a fighter's heart while providing for her family after her father's death. These characteristics were ingrained in her before she left District 12. So while Rue might have learned things in the training exercises, it seems as if she has good instincts and follows direction well, things she would have brought to the games with her. And as Katniss discovers, Rue is not unknowledgeable.
In Chapter 15, Katniss tells Rue that she is smart and a survivor. For instance, in the previous chapter, it was Rue's idea to drop the tracker jacker nest on the careers. Raised in an agrarian society, Rue has a confidence and knowledge born of living close to nature. The reader witnesses this in that Rue knows how to use plants to treat Katniss' stings from the jackers.
An innocent is harmless. He/she generally does not know a great deal about the world. Innocence is found in people without cunning, and they often lack knowledge and understanding. While this clearly applies to Prim, Rue is different. She is knowledgeable, and she has a clear understanding about her home district. The hardships Rue describes about District 11 make Katniss question whether her district is as terrible as Rue's.
After Rue dies, Katniss describes the connection she feels with Rue and Prim:
But I feel as if I did know Rue, and she'll always be with me. Everything beautiful brings her to mind. I see her in the yellow flowers that grow in the Meadow by my house. I see her in the Mockingjays that sing in the trees. But most of all, I see her in my sister, Prim.
Katniss may find Prim and Rue to be similar because both are young, defenselessness and vulnerable. Neither of the girls could survive alone. Katniss volunteers to take Prim's place to keep her safe. Katniss forms an alliance with Rue to keep her safe. When Rue is killed, Katniss observes Rue's vulnerability even in death:
I can’t stop looking at Rue, smaller than ever, a baby animal curled up in a nest of netting. I can’t bring myself to leave her like this. Past harm, but seeming utterly defenseless.
My perception is that Prim and Rue are symbolic of those unable to protect themselves. The games pit the fighters against the weak and vulnerable. This reflects the norms of the citizens of Panem: those able to entertain the citizens earn sponsors that give them a better chance to survive. The vulnerable participants are not impressive—killed off quickly: little more than sacrifices for the citizens' sport.
The symbolism of the characters of Rue and Prim may be found in the reader's realization that in every society, the weak are more apt to be preyed upon and must be protected by those who are stronger.